When arc welding, it is necessary to attach a ground to the object being welded while the other pole of the electric circuit is the welding rod. When the electricity passes through the welding rod to the object, it melts the tip of the welding rod thereby depositing molten metal on the object.
Usually a spring clamp is used to connect the ground cable from the welding apparatus to the object. Nuts on the top of the clamps are used to attach the lug of the ground cable to the clamps. In one common embodiment, a spring loaded terminal (refer to FIG. 3) is attached to a flat magnetic clamp. The spring loaded terminal has a bolt that passes through the middle of the magnet and abuts the object to be welded. In this fashion, the electric current does not pass through the magnet, but rather is shunted directly through the bolt.